System.Net.Http could not be resolved in the currently targeted framework .NET 4.0

Got a nasty error after moving a solution from Visual Studio 2010 to 2012. Build is fine and everything works perfect localhost. I have one new MVC4 project that requires .NET 4.5 so I installed the 4.5 framework on the build server. The build is good but MSBuild is failing to copy DotNetOpenAuth.Core.dll from its package location to the Bin dir. The issue is because, though the particular project targets the 4.0 framework, I believe MSBuild is checking the dependency against .NET 4.5 framework System.Net.Http assembly as part of its CoreBuild.

warning code="MSB3268" The primary reference \packages\DotNetOpenAuth.Core.4.3.0.13117\lib\net40-full\DotNetOpenAuth.Core.dll" could not be resolved because it has an indirect dependency on the framework assembly "System.Net.Http, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" which could not be resolved in the currently targeted framework. ".NETFramework,Version=v4.0". To resolve this problem, either remove the reference "c:\cc\kazork\code\trunk\src\packages\DotNetOpenAuth.Core.4.3.0.13117\lib\net40-full\DotNetOpenAuth.Core.dll" or retarget your application to a framework version which contains "System.Net.Http, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a

So even though I was copying System.Net.Http .NET 4.0 via the Nuget package that is added when installed the DotNetOpenAuth packages, MsBuild on my build server was checking the DotNetOpenAuth.Core dependency and checking against .NET assemblies installed on the machine not what was being copied to the Bin. In my case:

directory so I believe MsBuild attempted to look in the newly installed .NET 4.5 assemblies, on my machine..\Assemblies\Microsoft\Framework.NETFramework\v4.5 where there is a System.Net.Http.dll and that is why, instead of getting an outright error that System.Net.Http.dll for .NET 4.0 targets does not exist, I got a warning about DotNetOpenAuth.Core.dll's dependency on System.Net.Http, which can be found but is not for the 4.0 framework as the project was targeting.